Method and hardware for cleaning uv chambers

ABSTRACT

A cleaning method for a UV chamber involves providing a first cleaning gas, a second cleaning gas, and a purge gas to one or more openings in the chamber. The first cleaning gas may be an oxygen containing gas, such as ozone, to remove carbon residues. The second cleaning gas may be a remote plasma of NF 3  and O 2  to remove silicon residues. The UV chamber may have two UV transparent showerheads, which together with a UV window in the chamber lid, define a gas volume proximate the UV window and a distribution volume below the gas volume. A purge gas may be flowed through the gas volume while one or more of the cleaning gases is flowed into the distribution volume to prevent the cleaning gases from impinging on the UV transparent window.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Patent ApplicationSer. No. 61/692,674 filed Aug. 23, 2012, which is incorporated herein byreference.

FIELD

Embodiments described herein generally relate to methods and apparatusfor recovering dielectric constant of a low dielectric constantmaterial. A chamber having two UV transparent gas distributionshowerheads is described that allows cleaning of silicon and carbonresidues without affecting a UV window in the chamber lid.

BACKGROUND

As the size of the electronic devices is reduced, new materials with alow dielectric constant (k), such as materials with dielectric value aslow as 2.2, are used in forming the electronic devices.

Plasma-deposited porous low k films are one class of materials that isable to satisfy such a requirement. The presence of pores and carbon,which contributes to low dielectric value, creates significant processintegration challenges since the pores are susceptible to etching,ashing, and plasma damages. Therefore, a k-restoration process isusually needed to restore the porous low-k films after formation and/orafter integration.

Traditionally, two different chambers are needed for k-restoration. Onechamber for chemical treatment of the low-k films, such as silylation,or deposition of a thin film for surface treatment of the low-k films. Adifferent chamber is used for pore sealing using UV (ultra violet)curing. Traditional k-restoration is performed in separate chambersbecause the chemical surface treatment uses a showerhead to supply aprocessing gas including halogen or ozone while the UV chamber uses aquartz window which usually is not compatible with halogen and ozone.However, the two chamber k-restoration process increases cost ofownership by requiring two chambers and additional time for substratetransfer.

Therefore, there is a need for an improved apparatus and method fork-restoration processes.

SUMMARY

Embodiments disclosed herein generally relate to methods and apparatusfor processing substrates. A process chamber features a first UVtransparent showerhead and a second UV transparent showerhead. A UVtransparent window is positioned above the showerheads. The UVtransparent window and the first UV transparent showerhead togetherdefine a gas volume, and the first UV transparent showerhead and thesecond UV transparent showerhead together define a distribution volume.Gas openings in the chamber side wall or lid provide a flow pathway forprocess gases into the gas volume and/or the distribution volume.Process gases flow through the first and second UV transparentshowerheads into a space proximate to a substrate support.

A cleaning method for such a chamber involves providing a first cleaninggas, a second cleaning gas, and a purge gas to one or more openings inthe chamber. The first cleaning gas may be an oxygen containing gas,such as ozone, to remove carbon residues. A second cleaning gas may be aremote plasma of NF₃ and O₂ to remove silicon residues. A purge gas maybe flowed through the gas volume while one or more of the cleaning gasesis flowed into the distribution volume to prevent the cleaning gasesfrom impinging on the UV transparent window.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention may be had by reference to embodiments, some of which areillustrated in the appended drawings. It is to be noted, however, thatthe appended drawings illustrate only typical embodiments of thisinvention and are therefore not to be considered limiting of its scope,for the invention may admit to other effective embodiments.

FIG. 1 is a schematic sectional view of a process chamber 100 accordingto one embodiment.

FIG. 2A is a plan view of a UV transparent gas distribution showerheadaccording to one embodiment.

FIG. 2B is a plan view of a UV transparent gas distribution showerheadaccording to another embodiment.

FIG. 2C is a detailed cross-sectional view of a UV transparent gasdistribution showerhead according to another embodiment.

FIG. 2D is a plan view of a UV transparent gas distribution showerheadaccording to another embodiment.

DETAILED DESCRIPTION

FIG. 1 is a schematic sectional view of a processing chamber 100according to one embodiment. The processing chamber 100 is configured toprocess a substrate using UV energy, one or more processing gases, andremotely generated plasma.

The processing chamber 100 includes a chamber body 102 and a chamber lid104 disposed over the chamber body. The chamber body 102 and the chamberlid 104 form an inner volume 106. A substrate support assembly 108 isdisposed in the inner volume 106. The substrate support assembly 108receives and supports a substrate 110 thereon for processing.

A first UV transparent gas distribution showerhead 116 is hung in theinner volume 106 through a central opening 112 of the chamber lid 104 byan upper clamping member 118 and a lower clamping member 120. The UVtransparent gas distribution showerhead 116 is positioned facing thesubstrate support assembly 108 to distribute one or more processinggases across a distribution volume 122 which is below the first UVtransparent gas distribution showerhead 116. A second UV transparentshowerhead 124 is hung in the inner volume 106 through the centralopening 112 of the chamber lid 104 below the first UV transparent gasdistribution showerhead 116. Each of the UV transparent gas distributionshowerheads 116 and 124 is disposed in a recess formed in the chamberlid 104. A first recess 126 is an annular recess around an internalsurface of the chamber lid 104, and the first UV transparent gasdistribution showerhead 116 fits into the first recess 126. Likewise, asecond recess 128 receives the second UV transparent gas distributionshowerhead 124.

A UV transparent window 114 is disposed above the first UV transparentgas distribution showerhead 116. The UV transparent window 114 ispositioned above the first UV transparent gas distribution showerhead116 forming a gas volume 130 between the UV transparent window 114 andthe first UV transparent gas distribution showerhead 116. The UVtransparent window 114 may be secured to the chamber lid 104 by anyconvenient means, such as clamps, screws, or bolts.

The UV transparent window 114 and the first and second UV transparentgas distribution showerheads 116 and 124 are at least partiallytransparent to thermal or radiant energy within the UV wavelengths. TheUV transparent window 114 may be quartz or another UV transparentsilicon material, such as sapphire, CaF₂, MgF₂, AlON, a silicon oxide orsilicon oxynitride material, or another transparent material.

A UV source 150 is disposed above the UV transparent window 114. The UVsource 150 is configured to generate UV energy and project the UV energytowards the substrate support 108 through the UV transparent window 114,the first UV transparent gas distribution showerhead 116, and the secondUV transparent gas distribution showerhead 124. A cover (not shown) maybe disposed above the UV source 150. In one embodiment, the cover may beshaped to assist projection of the UV energy from the UV source 150towards the substrate support.

In one embodiment, the UV source 150 includes one or more UV lights 152to generate UV radiation. The UV lights may be lamps, LED emitters, orother UV emitters. More detailed descriptions of suitable UV sources canbe found in U.S. Pat. No. 7,777,198, and United States PatentPublication 2006/0249175.

The processing chamber 100 includes flow channels configured to supplyone or more processing gases across the substrate support 108 to processa substrate disposed thereon. A first flow channel 132 provides a flowpathway for gas to enter the gas volume 130 and to be exposed to UVradiation from the UV source 150. The gas from the gas volume 130 mayflow through the first UV transparent gas distribution showerhead 116into the distribution volume 122. A second flow channel 134 provides aflow pathway for gas to enter the distribution volume 122 directlywithout passing through the first UV transparent gas distributionshowerhead 116 to mix with the gas that was previously exposed to UVradiation in the gas volume 130. The mixed gases in the distributionvolume 122 are further exposed to UV radiation through the first UVtransparent gas distribution showerhead 116 before flowing through thesecond UV transparent gas distribution showerhead 124 into a spaceproximate the substrate support 108. The gas proximate the substratesupport 108, and a substrate disposed on the substrate support 108, isfurther exposed to the UV radiation through the second UV transparentgas distribution showerhead 124. Gases may be exhausted through theopening 136. Purge gases may be provided through the opening 138 in thebottom of the chamber, such that the purge gases flow around thesubstrate support 108, effectively preventing intrusion of process gasesinto the space under the substrate support.

The first UV transparent gas distribution showerhead 116 includes aplurality of through holes 140 that allow processing gas to flow fromthe gas volume 130 to the distribution volume 122. The second UVtransparent gas distribution showerhead 124 also includes a plurality ofthrough holes 142 that allow processing gas to flow from thedistribution volume 122 into the processing space proximate thesubstrate support 108. The through holes in the first and second gas UVtransparent gas distribution showerheads may be evenly distributed withthe same spacing or different spacing.

FIG. 2A is a plan view of the first UV transparent gas distributionshowerhead 116. The first showerhead 116 may comprise a first pluralityof through holes 202 arranged toward a periphery of the first showerhead116 and a second plurality of through holes 204 arranged toward a centerregion of the first showerhead 116. The first plurality of through holes202 and the second plurality of through holes 204 may be arranged inconcentric ranks. In the embodiment of FIG. 2A, the through holes 202 atthe periphery of the showerhead 116 have a diameter that is larger thanthe holes 204 at the central region of the showerhead 116. In oneembodiment, the holes 202 have a diameter between about 0.020 inches andabout 0.050 inches, for example about 0.030 inches, and the holes 204have a diameter between about 0.010 inches and about 0.030 inches, forexample about 0.020 inches. The holes 202 have a first spacing 220, andthe holes 204 have a second spacing 210. In the embodiment of FIG. 2A,the spacing 210 is larger than the spacing 220. In the embodiment ofFIG. 2A, the hole size and spacing promotes faster flow through theshowerhead 116 in the peripheral region thereof to promote contact ofcleaning gases with chamber walls.

FIG. 2B is a plan view of the second UV transparent gas distributionshowerhead 124. The showerhead 124 may comprise a plurality of throughholes 206 with uniform size and spacing to promote uniform flow throughthe showerhead 124. The through holes 206 may have a diameter of betweenabout 0.020 inches and about 0.050 inches, for example about 0.030inches.

FIG. 2C is a detailed cross-sectional view of a UV transparent gasdistribution showerhead 200 having through holes 208 formed therein. Thethrough holes 208 may be used as the through holes 140, 142, 202, and204, and the plate 200 may be used as the plate 116 or 124. The throughholes 208 have a tapered entry portion 222 and a tapered exit portion224. A coating 226 is disposed over all exposed surfaces of the plate200. The coating 226 may be a fluorine-resistant coating, such assapphire, CaF₂, MgF₂, AlON, or other fluorine-resistant material, and istypically conformal. The coating may have a thickness between about 1 μmand about 10 μm, and may be deposited by a vapor deposition process,such as chemical vapor deposition, which may be plasma enhanced. Thetapered entry portion 222 and the tapered exit portion 224 facilitatecoating the entire surface of the through hole 208. IN the embodiment ofFIG. 2C, both major surface of the plate 200 are coated. In an alternateembodiment, only one major surface of the plate 200 is coated. In suchan embodiment, the through holes 208 may be entirely coated or onlypartially coated. In another alternate embodiment, the through holes 208are tapered on only one side, the entry side or the exit side.

FIG. 2D is a plan view of a second UV transparent gas distributionshowerhead 250 according to another embodiment. The showerhead 250 maybe used in the apparatus 100 of FIG. 1 as the showerhead 124. Theshowerhead 250 has a single large opening 255 in a central region of theshowerhead 250. The opening 255 allows flow through the showerhead 250,and sizing of the opening 255 relative to a substrate to be processed inthe chamber 100 (FIG. 1) promotes uniform processing of the substrate.For a 300 mm circular substrate, sizing the opening 255 at a diameter ofabout 0.5 inches allows uniform processing of substrates and thoroughcleaning of chamber surfaces.

In operation, processing gases are provided to the gas volume 130 andthe distribution volume 122 and pass through the showerheads 116 and 124to perform a material operation on a substrate disposed on the substratesupport 108. Residues of the process gases impinge on various chambersurfaces, such as the window 114, on a side facing the gas volume 130,either side of the showerheads 116 and 124, and the chamber walls. Inone aspect the residues contain carbon and silicon.

A method of removing carbon and silicon residues from a chambercontaining quartz or silicon oxide components, such as the chamber 100with the UV transparent window 114, includes providing a first cleaninggas to the gas volume 130 and/or the distribution volume 122 through theopenings 132 and 134. The first cleaning gas may comprise an oxygencontaining gas, such as ozone (O₃) for removing carbon residues. Thefirst cleaning gas may also be flowed through the opening 138 and aroundthe substrate support 108, exiting through the exhaust opening 136, toremove carbon residue from the lower surfaces of the chamber 100. The UVsource 150 may be activated during the cleaning process to promoteformation of oxygen radicals from oxygen in the oxygen-containing gas,thus improving carbon removal.

A second cleaning gas may be provided to the chamber 100 to removesilicon and carbon residues concurrently. The second cleaning gas isselected to remove silicon residues while not reacting with siliconoxide components of the chamber 100, such as a quartz window 114. Thesecond cleaning gas may be a fluorine-containing gas, which may beactivated outside the processing chamber. In one example, the secondcleaning gas is a remote plasma of NF₃ and O₂ containing oxygen radicalsand fluorine radicals. The UV source may be activated during use of thesecond cleaning gas to promote formation of oxygen radicals and thebreak diatomic fluorine into fluorine radicals. The second cleaning gasmay also be provided through the openings 132, 134, and 138, exhaustingthrough the opening 136.

A purge gas, such as argon or helium, may be provided through theopening 132, instead of a cleaning gas. During a material operation, apurge gas may be provided through opening 132 while a precursor gas isprovided through opening 134. The purge gas prevents deposition ofprocess gases on the UV window 114 by confining the process gases to thedistribution volume 122. During a cleaning operation, a purge gas maylikewise be used in the gas volume 130 if cleaning is not required forthe UV window 114. In another embodiment, purge gas may be providedthrough the openings 132 and 134, while a cleaning gas is providedthrough the opening 138 to perform a cleaning operation on lowersurfaces of the chamber 100. In such an embodiment, the substratesupport 108 may be moved to a position proximate the second recess 128of the chamber lid 104 to promote energetic flow of purge gas around theedge of the substrate support 108 into the exhaust opening 136,effectively preventing cleaning gases from emerging into the spacebetween the second showerhead 124 and the substrate support 108.

When a remote plasma of NF₃ and O₂ is used as the cleaning gas, thepurge gas may be argon remote plasma. When used as a purge gas duringcleaning, the argon plasma may be subjected to a high pressure drop whenentering through the openings 132 and/or 134 to promote recombination ofradicals, while the cleaning gas is subjected to a low pressure drop topromote radical longevity.

Table 1 contains a summary of a typical cleaning matrix, according tothe methods described herein.

TABLE 1 Clean First Cleaning Second Treat Frequency Step Cleaning StepInterval Every Every Multiple Multiple substrate substrate or substratessubstrates multiple Opening 132 Helium Helium Argon Argon Opening 134Helium O₃ NF₃/O₂ RPS Argon low conc. Opening 138 Helium O₃ NF₃/O₂ RPSNF₃/O₂ RPS low conc. low conc. UV Intensity High High Low Low SpacingNormal Wide Normal Close

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. An apparatus for processing a substrate, comprising: a chamberenclosing a substrate support; a UV source positioned to illuminate thesubstrate support; and a chamber lid, comprising: a window substantiallytransparent to UV radiation between the UV source and the substratesupport; a first showerhead between the window and the substratesupport, the first showerhead comprising a plurality of through holeswherein a size of the through holes is larger at a periphery of theshowerhead than at a central portion of the showerhead; and a secondshowerhead between the first showerhead and the substrate support. 2.The apparatus of claim 1, wherein the chamber lid further comprises afirst gas flow channel between the window and the first showerhead and asecond gas flow channel between the first showerhead and the secondshowerhead.
 3. The apparatus of claim 2, wherein the chamber lid furthercomprises a first annular recess that receives the first showerhead anda second annular recess that receives the second showerhead.
 4. Theapparatus of claim 3, wherein each of the first and second showerheadsis substantially transparent to UV radiation.
 5. The apparatus of claim4, wherein at least one of the first showerhead and the secondshowerhead has a coating.
 6. The apparatus of claim 1, wherein theplurality of through holes comprises a first plurality of through holesat a peripheral region of the first showerhead and a second plurality ofthrough holes at a central region of the first showerhead, wherein eachthrough hole of the first plurality has a first size and each throughhole of the second plurality has a second size, and wherein the firstsize is larger than the second size.
 7. The apparatus of claim 6,wherein the first plurality of through holes has a first spacing, thesecond plurality of through holes has a second spacing, and the secondspacing is larger than the first spacing.
 8. The apparatus of claim 7,wherein the through holes of the first plurality are arranged inconcentric circular ranks and the first spacing is a spacing between theconcentric circular ranks of the first plurality, and wherein thethrough holes of the second plurality are arranged in concentric ranksand the second spacing is a spacing between the concentric circularranks of the second plurality.
 9. The apparatus of claim 8, wherein thesecond showerhead comprises a third plurality of through holes havinguniform size and spacing.
 10. The apparatus of claim 9, wherein each ofthe through holes of the first and second showerheads has a side wall,and at least one of the first showerhead and the second showerhead has aconformal coating over at least the side wall of each through hole. 11.An apparatus for processing a substrate, comprising: a chamber enclosinga substrate support; a UV source positioned to illuminate the substratesupport; a window separating the UV source from the substrate support; afirst showerhead between the window and the substrate support, the firstshowerhead having a first plurality of through holes at a peripheralportion thereof and a second plurality of through holes at a centralportion thereof, wherein each through hole of the first plurality ofthrough holes has a first diameter, each through hole of the secondplurality of through holes has a second diameter, the first diameter islarger than the second diameter, the first plurality of through holeshas a first spacing, the second plurality of through holes has a secondspacing, and the first spacing is smaller than the second spacing; and asecond showerhead between the first showerhead and the substratesupport, wherein the second showerhead has a third plurality of throughholes with uniform size and spacing, wherein the first and secondshowerheads are each substantially UV transparent.
 12. The apparatus ofclaim 11, wherein at least one of the first showerhead and the secondshowerhead has a coating.
 13. A method of cleaning a process chamberhaving an interior space, comprising: providing a purge gas to a firstportion of the interior space; providing a first cleaning gas to asecond portion of the interior space; activating the first cleaning gasusing UV radiation from UV lamps positioned outside the process chamber;providing a second cleaning gas to the second portion of the interiorspace; activating the second cleaning gas using the UV radiation; andexhausting the purge gas, the first cleaning gas, and the secondcleaning gas through a side wall of the chamber.
 14. The method of claim13, wherein the first cleaning gas is an oxygen-containing gas and thesecond cleaning gas is a fluorine-containing gas.
 15. The method ofclaim 14, wherein the second cleaning gas is a remote plasma.
 16. Themethod of claim 15, wherein the second cleaning gas comprises NF₃ andO₂.
 17. The method of claim 16, wherein the first cleaning gas comprisesO₃.
 18. The method of claim 17, wherein the purge gas flows from thefirst portion to the second portion to mix with the first cleaning gasand the second cleaning gas.
 19. The method of claim 18, wherein thepurge gas comprises helium or argon.